I did my last cure fire today, got up to 750-770F. Cracks appeared to have gotten wider, and now i can see through the crack at one area. I can see the fire ever so slightly, Structurally i guess it will be okay and i know it will still function as it should. My question is how do i repair it and what is the best way? Heat it up, have the cracks open up, grind out the cracks, widen the cracks and fill the cracks back in?. Now what do i use? Heatstop50? Rutland cement? Rutland gasket cement?. I have a bottle of the Rutland gasket cement which is good for 2000F, however i dont think that will be safe for food. I would really appreciate the help guys.

V-wiz, have you insulated?
Here is where I'm headed.. Whatever you do to patch the cracks will not be structural or at least not very. I think I'd mix a small batch of render, just enough to fill these cracks. Insulate the dome with your blanketing start working on the finishing of the igloo or house. The insulation will not burn and it will stop these cracks from venting. The other thing it will do for you is to even out the dome temps and so minimize the stresses that promote cracking.

My opinion is that once you start curing above 250F there are advantages for loosely covering the dome with insulation. One of these advantages is promoting a more even heating of the dome and so minimizing cracking. This is my opinion and it's just theory... and you're far past 250F and your dome is ready to cook, so no matter what you need to insulate and weatherize..

Thats what i was thinking. I just purchased Rutland fireplace mortar, it says for repairing cracked and chipped firebrick and repoint mortar joints. Also good for 2000f. Its basically what i want to do. So ill widen the cracks and fill it in.

Good luck, I've found crack repairs to never be particularly successful. But you'll need to get some moisture back into the crack before attempting a repair. Try making a thin slurry of pure calcium aluminate cement and get it onto the mating surfaces after the water, then fill with your heatstop.

I'm an advocate of curing t he oven after insulation because if the dome is uncovered there is a huge temperature difference between the inside temp and the outside temp which may have bee n the cause of your cracks.
What was the outside ambient temperature at the time you were firing?

Looking at the first photo on this thread it seems as though you have a lot of coinciding vertical joints, this could also be a contributor.

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